Note: I really don’t see anything but J1 games anymore (hence my post about what to do as America against J1), unless we’re playing with someone new (always the most fun games).
Anwyay, a bit late, but:
I basically agree with what Cow said, like I usually do. I wish I could find something I could disagree on with him, as it’s getting tiring :p
As the others said. Do what you’d normally do. Let’s go at this from the reverse side. Let’s say America does come to Europe:
If America immediately comes over to Europe to start fully messing with Germany, I mean 90%+ investment, that sucks, sucks real bad for Germany. I’ve never seen a KGF strategy in global, but I bet the US/UK/Russians could crumple Germany, like a wad of paper, to 35/turn or less by turn 5 or 6 with no problems at all (but definitely not take Berlin for a good while longer), and Italy is likely to be make crap-all as well. There’s just too many allied NPCs for the Axis to do anything about it. You just have to hope your Japanese player is doing his thing, and with that kind of game, my god, he can do whatever he wants. The Pacific victory is nearly guaranteed, actually.
So, since we have established that America can’t afford to do that, let’s assume a partial investment:
Don’t suicide yourself on a Sea Lion, but if UK leaves it super open, do it. Hopefully Italy can make some strong headway in the Med if you do. If America has to come over to liberate UK, and you’ve not hamstrung yourself by doing it, that’s fantastic for Japan. But again, only do Seal Lion if UK has gift-wrapped it for you.
I’d say the safest bet is just go straight for Moscow and keep your western flank as protected as you can. If you can’t take Moscow, at least shut down its economy, attempt to lock down some of the british airforce on Moscow to defend it, and get as much money as you can. Hopefully you’re taking either Moscow or the middle east by turn 7-9, depending on what all happens, so that you’re not completely relying on Japan. Remember, if you’re playing with partial but heavy (50%+) investment of America in Europe, you’re basically just playing A&A 1940 Europe, except you got 2 more IPCs from the fall of France, Russia made an extra 9 IPCs for the turns you weren’t at war (so declare war on I2 or G3, at the latest!), there’s one more inf in Egypt, and America is showing up to the party a turn earlier. Is it harder? Yeah, probably (depending on the level of US investment). Is it “hopeless”? Hell no. And with this kind of US investment in Europe, Japan is going to have an easy game.
The best part about it all is, since the US is always 2 turns away, no matter what they do, you’ll have an entire turn to do something about it. If you see heavy US buys in the Atlantic, you know you have plenty of time to keep your air force in range and to build some mechanized infantry in western germany to kick some invaders out (and defend your major IC). The US nearly always has to head to Gibraltar first. You nearly always have time to adapt.
Final note on the defense of Scandinavia:
As for the defense of Norway, I like to keep my Finns in Finland, only sending 1-4 Scandinavian infantry toward Stalingrad, depending. If they take Norway, you can use your little group of inf to smash into Norway (along with two units on your hopefully still-living transport) along with your air force. If they bring too much of a landing party for you to handle, especially if the British help, then you should at least be able to use your air, your cruiser, and hopefully some other surviving boat or boats (and the 1-6 new subs you bought in the Baltic when you saw the allies mass on Gibraltar or off the coast of the UK) to kill their navy, including their transports.
This should force the Allies into making a risky play, or having them go after Italy first, which is a better, or at least more workable, situation for the Axis than losing Scandinavia forever.
Added bonus: If the Allies do a neutral crush, you’ve already got people right there to claim Sweden. With the Finns and the Swedes parked there, Norway is basically a fortress for the rest of the game. If the Axis do a neutral crush, you’re already right there to hit Sweden (with the help of air, of course).
If you’re worried about a UK/US 1-2 punch on Denmark and then your Baltic fleet (and your 1-6 subs you just bought, see above), then Britain has spent a lot of money on boats or bombers, and Germany has lots of problems that will lead to faster crumpling. That situation is too complex to address here, but it’s still not hopeless. It largely involves praying that your Japanese player is winning :p